Part of a wider housekeeping effort on the packages repository.

Signed-off-by: Alberto Bursi <alberto.bursi@outlook.it>

libcurl is added as dependency for gnupg-util to avoid a dependency
error.

The following invalid configuration options are removed:
  --disable-ftp
  --enable-fake-curl

Fixes: 0a61d56eb3 ("utils/gnupg: add new package gnupg-utils")
Reported-by: Hannu Nyman <hannu.nyman@iki.fi>
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

The current package gnupg does not allow to receive keys due to
disable-exec, disable-hkp configuration.

The patch removes these switches. To avoid unduely increasing the package
size the helper executables are put into a new package gnupg-utils.

The version is bumped to 1.4.20 to avoid an error when receiving keys.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

Signed-off-by: Nicolas Thill <nico@openwrt.org>

Signed-off-by: Ian Leonard <antonlacon@gmail.com>

- update to latest version (v1.4.18)
 - add license info
 - add myself as maintainer

Signed-off-by: Nicolas Thill <nico@openwrt.org>